Phase 7e: polymorphic print(x) + str(x) (retire print_int/print_str)

One `print` instead of two C-style names: `print(x)` writes an int OR a string
followed by a newline, dispatching on the operand type (int -> %d, string ->
%s). `print(int)` emits byte-identically to the old print_int, so every existing
call and every smoke-test output is unchanged.

print_str was only ever the raw IR-to-stdout dump in ir_flush (no newline), which
is not "printing a line" — so it now uses file_write to a new file_stdout()
stream, keeping the emitted IR byte-for-byte identical. That frees `print` to
have consistent always-newline semantics.

Two reseeds: (A) add print + str + file_stdout keeping the intrinsics; (B)
migrate the 61 print_int calls to print, ir_flush to file_write(file_stdout()),
and delete print_int/print_str (+ the now-dead @.fmt_str). str(x) (the
interpolation converter from 7d) is now also a documented standalone builtin.

Vocabulary: print/str/file_stdout in, print_int/print_str out (ludic_syntax.h,
grammar, LudicTokens.kt). LANGUAGE.md updated. Reseeded (22551 lines); C-free
fixpoint holds; goldens identical; 18/18; vocab + doc-fences clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

selfhost/emit_decl.ludic

@@ -94,9 +94,10 @@ fn emit_program() -> void {
 fn ir_flush(path: ptr) -> bool {
   let h = buf_str(head)
   let c = buf_str(code)
-  if (path == null) {
-    print_str(h)
-    print_str(c)
+  if (path == null) {                             # raw IR to stdout (no trailing newline)
+    let out = file_stdout()
+    file_write(out, h, slen(h))
+    file_write(out, c, slen(c))
     return true
   }
   let f = file_open(path, "wb")